1. Field of the Invention
A toll restrictor is disclosed for use with time division multiplex switching systems. In particular, the toll restrictor includes means for decoding TDM signals, comparing the decoded signals with memories of restricted codes and allowing or denying connections from calling lines to called lines.
2. Description of the Prior Art
Toll restrictors of many types are known in the telephone art and their functions are, of course, well-known. The present toll restrictor is especially adapted for use with a time division telephone switching system which may be of the type shown in U.S. Pat. No. 3,941,936 issued Mar. 2, 1976, as filed Oct. 4, 1974 in the name of Graham et al. and assigned to the assignee hereof.
In that system each circuit function is allotted to specific time slots. Thus, each register, each local link and each trunk has separate time slots assigned to it. A recirculating memory stores calling and called numbers using the time slots for call processing and for speech during a call. No provisions were made in this prior art to enable the restriction of calls to particular calling subscribers.